I have kept a very small backyard flock for close on twenty years but I am puzzled by the recent unexpected deaths of two of my flock. They were full of health in the morning and dead with no signs of injury in the afternoon. They died a week apart. The county ag agent had no suggestions and said an autopsy would be costly. I have searched my yard for a cause but have found none. I am down to one lonely chicken and have to decide whether to get new chicks or find her a home. Any thoughts on the matter?

Well if your chickens were around 20 years they might have just grown old. I read something saying that a normal lifespan for a chicken is 15 years. I dont know what else is could have been hope this helps a little.

Thanks for the responses to Eureka chick. I guess I wasn't clear. My chickens were not 20 years old. One was six and the other was two. What I meant was that in my twenty years of keeping a backyard flock I have never had birds die so suddenly with no apparent cause. I'm concerned about poisoning. I was curious to see if anyone else may have had a similiar experience. The longest I've had a chicken live was 13.

Eureka,
What state are you in? Some states will do a free necropsy for backyard flocks.
If I were you, I'd take a fecal sample in to the vet for a float to see if your flock has worms.
Did you notice anything strange about the two who died? Stumbling, depression, weight loss, anything?

Thanks for your input. The trouble is they had no symptoms. The first death I thought "oh my, she had a heart attack or stroke" But when the second one died a week later it was too coincidental. Both birds were vigorous, there combs were bright red, they ate well and were active, no unusual stools. My main concern is that they died from poisoning but it would have to have been fast acting. (4-6 hours) They have a large backyard with plantings to roam in. I checked my recently introduced plants but they're non toxic and there was no evidence of nibbling. At one point I was worried that someone had thrown rat poison over the fence, but found no evidence of that either. I live in northern California and the local ag extension told me it would be very costly to autopsy. I guess I won't ever know what killed them. I just didn't want to put any new chickens in harm's way.

you can do a home autopsy, I have done this for a number of my birds and it helps give me a narrower range of things to read up on (usually) theres a link here - this site gives you step by step instructions and also a list of possibilities based on your findings at the end.

It can be hard to do on a bird that's been well loved but it can really help with either reassurance or information (or both)

Thank you all. I am suprised to hear that Davis would do a free necropsy since my local ag agent in Eureka (the far north coast) seemed to indicate otherwise. Maybe he was refering to the cost of expediated shipping. I think I was somewhat in shock and grief stricken when I found my second hen. I briefly considered trying to squeeze her into our tiny freezer on the chance of getting a necropsy but I knew that would compound my partner's shock. Although logically I knew it might be a good idea, I couldn't bring myself to cut her open myself. I wouldn't know what I was looking at and my partner would totally flip out to find me cutting into our beloved pet. I ended up burying her.
Of course there is the guilt of not doing enough to protect them from whatever it was that killed them. I am trying to move past that. I have a new resolve. I appreciate this site and all the wonderful people who participate in it.